Defective phospholipid metabolism in the retinular cell membrane of norpA (no receptor potential) visual transduction mutants of Drosophila.

The phosphorylation of photoreceptor phospholipids in the three alleles of Drosophila visual mutants (norpA: no receptor potential A gene) was studied. In the normal strain, the gamma-32P of ATP was transferred mainly to phosphatidic acid (PA) and diphosphoinositide (DPI), while, in the mutants, we found that the phosphorylation of PA was drastically reduced, but that of DPI was not. The radioactivity incorporation into PA closely parallels with the degree of the mutant genes' expressivity among the three alleles of norpA tested. Therefore, the abnormality found in the phosphorylation of diglycerol to PA may be closely related to the primary mutant defect in the phototransduction mechanism.